Line 18 transgenic mice are viable, fertile, normal in size, and do not display any gross physical or behavioral abnormalities. NOD transgenic females exhibit reduced diabetes incidence (45%) by 40 weeks of age and more rapid insulitis onset (50%, severe infiltration) at 12 weeks of age compared with NOD controls (80% diabetic by 40 wk and 20% insulitis-positive at 12 weeks). Intra-islet lymphocytes expressing interferon gamma were 50 times more frequent in sections from transgenic Line 18 than in wild-type controls, while IL4 stained cells were barely detectable in either.